1. Field of the Invention
The present invention relates to a position reporting device for determining and reporting the position of a person or an object, and more specifically, to a controllable external-to-internal antenna switch algorithm and circuit that enhances the functionality of the position reporting device.
2. Discussion of the Prior Art
The prior art position reporting devices are useful to locate and report the position of a person or object. A typical position reporting device comprises a navigation system such as the Global Positioning System (GPS) module and a mobile communications system such as a cellular modem.
The TrimTrac™ locator manufactured by Trimble Navigation Ltd, located at Sunnyvale, Calif., is a mobile tracking device that provides vehicle monitoring, security and recovery services to a broad number of subscribers. The TrimTrac locator device includes a GPS receiver and GSM modem that are integrated onto a single board and are controlled by a common microprocessor. A typical TrimTrac™ locator device includes two antennas: an internal GPA antenna and an external GPS antenna. However, only one antenna can be powered at the same time to avoid interference between the received GPS signals.
What is needed is to establish a procedure that would allow the TrimTrac™ locator the optimal usage of its two antennas.